LONDON, May 10 (Reuters) - Barclays Chief Executive Jes Staley faced calls from individual shareholders to resign and received lukewarm backing in a vote to reappoint him at the bank's annual general meeting, following his attempts to unmask a whistleblower.

The British bank said last month it had reprimanded Staley and would cut his bonus after he twice attempted to identify the author of a letter that revealed "concerns of a personal nature" about an unnamed senior employee.

Staley faced much higher than usual abstentions at the Barclays annual general meeting on Wednesday, with only 62 percent of possible votes cast. This compared with more than 70 percent for the lender's other board members in a sign of investor concerns after ISS, a shareholder proxy firm, last month advised them to abstain on Staley's board re-election.

However, of those votes that were cast rather than withheld, 97 percent were in favour of Staley's reappointment and he got a public endorsement from Chairman John McFarlane, who said that he was standing by the chief executive.

"You know me, if I thought he should go he would have gone," McFarlane told investors.

Shareholders questioned how Staley could not have been aware of the lender's policies prohibiting such attempts to unmask whistleblowers, and said his actions brought shame on the bank.

"Will you act now with integrity and honour and resign," shareholder Michael Mason-Mahon, a frequent activist at major British banks' annual general meetings, asked Staley at Barclays' own AGM in London's Royal Festival Hall.

"I made a mistake in becoming involved in an issue which I should have left to the business to deal with," Staley said.

McFarlane said Staley made a mistake but not one that should cost him his career.

"The action of going through a red light is not that you lose your licence," McFarlane said.

McFarlane told reporters after the meeting that Staley had the backing of the bank's entire board, after they discussed how to handle his attempts to find out who was sending the letters criticising a Barclays executive.

Staley also did nothing wrong in relation to a dispute with private equity firm KKR & Co and Staley's brother-in-law, McFarlane said.

That dispute, another headache for the Barclays CEO, revolves around Staley's actions on behalf of his brother-in-law Jorge Nitzan after a deal between him and the buyout firm went sour.

Staley told the AGM that he did not see a need for Barclays to shift jobs or significant operations out of Britain as a result of the country's vote last June to leave the European Union, regardless of how the exit negotiations pan out.

Barclays shares were 2 percent higher by 1452 GMT, the third best performer in the STOXX Europe 600 banks index. (Editing by Alexander Smith)